FIG. 22 and FIG. 23 illustrate an example of a conventionally known steering apparatus. This steering apparatus has a function for allowing adjustment of the up-down position and the forward-backward position of the steering wheel 1 according to the body size and driving posture of the driver, a function for reducing the force required by the driver to operate the steering wheel 1, and a function for allowing displacement of the steering wheel 1 in the forward direction when a secondary collision occurs and the body of the driver collides with the steering wheel 1 during a collision accident. In this specification, the forward-backward direction, the left-right direction and the up-down direction, unless specified otherwise, mean the forward-backward, the left-right and the up-down direction of a vehicle respectively.
This kind of steering apparatus has: a steering shaft 2, the steering wheel 1 being fastened to the rear-end section thereof; a steering column 3 that supports the steering shaft 2 on the inside thereof so as to be able to rotate freely; a steering force auxiliary apparatus 4 that applies an auxiliary torque to the steering shaft 2; and a steering gear unit 6 for causing a pair of left and right tie rods 5 to displace (pushes or pulls) based on the rotation of the steering shaft 2.
The steering shaft 2 is constructed by fitting the front-end section of an outer shaft 8 that is located on the rear side around the rear-end section of an inner shaft 7 that is located on the front side so that rotational force can be freely transmitted, and so that sliding movement in the axial direction is possible. Moreover, the steering column 3 is constructed by fitting the front-end section of an outer column 10, which is a rear-side column that is located on the rear side, around the rear-end section of an inner column 9, which is a front-side column that is located on the front side, so that sliding movement in the axial direction is possible. With the inner shaft 7 and the outer shaft 8 displacing relative to each other in the axial direction, and with the inner column 9 and the outer column 10 displacing relative to each other in the axial direction, it is possible to adjust the forward-backward position of the steering wheel 1, and it is possible for the entire length of the steering shaft 2 to contract during a collision accident.
The front-end section of the inner column 9 is joined and fastened to the rear-end surface of a gear housing 11 of the steering force auxiliary apparatus 4. Moreover, the inner shaft 7 is inserted into the gear housing 11, and the front-end section of the inner shaft 7 is connected to an input shaft of the steering force auxiliary apparatus 4. Furthermore, the front-end section of an output shaft 12 of the steering force auxiliary apparatus 4 that is connected to the input shaft by way of a torsion bar protrudes from the front-end surface of the gear housing 11.
The inner column 9 is supported by the vehicle body 13 so as to be prevented from displacing in the axial direction, and so as to only be able to pivot around a tilt pivot shaft 14 that is arranged in the left-right direction (front-back direction in FIG. 22) of the vehicle body 13. In the example in the figures, the tilt pivot shaft 14 is supported by the vehicle body 13 by way of a front support bracket 15, and is inserted into a support cylinder 16 that is provided on the upper part of the front end of the gear housing 11. Therefore, the inner column 9 does not displace in the forward direction even during a secondary collision.
On the other hand, the middle section of the outer column 10 is supported by part of the vehicle body 13 by a rear support bracket 17 so at to be able to detach (drop) in the forward direction when a strong impact is applied in the forward direction. In order to accomplish this, as illustrated in FIG. 23, a pair of installation plate sections 19 that protrude to the sides of the steering column 3 are provided on the top-end section of a pair of sidewall sections 18 of the rear support bracket 17, and notches 20 that are open to the rear-end edge of the installation plate section 19 is provided in each of the installation plate sections 19. Capsules 21 that are fastened to the vehicle body 13 by bolts (not illustrated in the figure) are locked in the notches 20. These capsules 21 have through holes 22 in the middle section thereof for inserting bolts.
During a collision accident, when a secondary collision occurs in which the body of the driver collides with the steering wheel 1, a large impact load is applied in the forward direction to the steering column 3 by way of the steering shaft 2. And the steering shaft 2 and the steering column 3 have a tendency to contract the entire length of them. In other words, the rear support bracket 17 tries to displace in the forward direction with the outer column 10, however, the pair of capsules 21 are stayed in place by the bolts. As a result, the capsules 21 come out in the backward direction from the notches 20, which allows the steering wheel 1 to displace in the forward direction.
Moreover, in order to allow adjustment of the forward-backward position and the up-down position of the steering wheel 1, the outer column 10 is supported by the rear support bracket 17 so as to be able to move in the forward-backward direction and the up-down direction. More specifically, a supported bracket 23 is welded and fastened to the bottom surface in the middle section of the outer column 10, and this supported bracket 23 is held by a pair of left and right sidewall sections 18 of the rear support bracket 17. Furthermore, forward-backward long holes 24 that extend in the forward-backward direction are formed in portions of left and right sidewalls of the supported bracket 23 that are aligned with each other. On the other hand, up-down long holes 25 that extend in the up-down direction are formed in portions of the sidewall sections 18, that are aligned with each other such that the up-down long holes 25 are aligned with part of the forward-backward long holes 24. An adjustment rod 26 is inserted through the forward-backward long holes 24 and up-down long holes 25, and an adjustment nut 27 is screwed onto a male screw section on the tip end section of the adjustment rod 26 that protrudes to the outside from one of the sidewall sections 18 (left side in FIG. 23). In this state, an outward facing flange shaped head section 28 that exists on the base-end section of the adjustment rod 26 engages with the up-down long hole 25 that is formed in the other sidewall section 18 (right side in FIG. 23) so as to be able to move up and down.
The adjustment nut 27 can be freely turned by an adjustment lever 29. Therefore, by rotating the adjustment nut 27 by operating the adjustment lever 29 and changing the spacing between the adjustment nut 27 and the head section 28 of the adjustment rod 26, the steering column 3 (outer column 10) to which the supported bracket 23 is fastened can be fastened to or released from the rear support bracket 17. When the spacing between the adjustment nut 27 and the head section 28 is widened, it is possible to adjust the forward-backward position of the steering wheel 1 by moving the steering column 3 (outer column 10) in the forward-backward direction within the displaceable range in which the adjustment rod 26 can displace inside the forward-backward long holes 24. Moreover, it is possible to adjust the up-down position of the steering wheel 1 by moving the steering column 3 within the displaceable range in which the adjustment rod 26 can displace inside the up-down long holes 25. When doing this, the steering column 3 pivotally displaces in the up-down direction around the tilt pivot shaft 14.
The rear-end section of the intermediate shaft 31 is connected to the front-end section of the output shaft 12 of the steering force auxiliary apparatus 4 by way of a universal joint 30. An input shaft 33 of the steering gear unit 6 is connected to the front-end section of the intermediate shaft 31 by way of another universal joint 32. The input shaft 33 is connected to the pinion of the rack and pinion (not illustrated in the figure) of the steering gear unit 6. The tie rods 5 are connected to both the left and right end sections of the rack that engages with the pinion, and by pushing and pulling the tie rods 5 on both sides according to the displacement in the axial direction of the rack, a desired steering angle is applied to the left and right steered wheels. Moreover, the steering force auxiliary apparatus 4 transmits the rotation of an electric motor 34, which is a power source, to the output shaft 12 by way of a worm reducer that is provided on the inside of the gear housing 11, and applies an auxiliary torque having a specified size in a specified direction to the output shaft 12.
Electric equipment such as a steering lock apparatus, combination switch and the like are installed at the rear-end section of the outer column 10. The rear-end section of cables such as power lines and signal lines are connected to this electric equipment, however, these cables are in the form of a cable harness that bundles the cables except the rear end sections, and this cable harness is covered with an insulating material. Cables such as these are arranged so as to run along the steering column 3 in the forward-backward direction. In order for this, a cable support bracket that is used for supporting the middle section of the cable is provided on part of the steering column 3 or a member that is located near the steering column 3, as typically done in the past. For example, JP 2010-116008 (A) discloses a structure in which a cable support bracket is provided on the side end section of a rear support bracket that supports the outer column.
On the other hand, a structure in which an impact energy that is applied to the steering wheel 1 from the body of the driver is absorbed by an energy-absorbing member plastically deforming as the steering wheel 1 displaces in the forward direction during a secondary collision has heretofore been known. For example, JP 2009-83611 (A) discloses a structure in which an energy-absorbing member that is made using metal plate plastically deforms due to an impact load that is applied to the steering wheel during a secondary collision. When applying a structure such as this, when the steering wheel 1 displaces in the forward direction, the cable tightens or stiffens in the axial direction and acts like a stopper rod between the inner column 9 or a member fastened to the inner column 9 and the outer column 10 or a member fastened to the outer column 10, which are supposed to displace relative to each other, and becomes a resistance against the displacement of the steering wheel 1 in the forward direction. As a result, there is a possibility that the impact absorbing performance by the plastic deformation of the energy-absorbing member will not be achieved as desired.